Check connectors in Office 365
If your email account was compromised, you'll need to check for malicious connectors that can affect your ability to send and receive messages.
Note: This has to be done from an Office 365 admin user account.
- Sign in to the Microsoft Exchange Admin Center.
- Select connectors under mail flow.
- If you don't recognize the connectors listed, select the connector and then the trash can button to remove them.